Electrosurgery is a technique used in the medical arts for cutting, ablation and coagulation of tissues. In electrosurgery, electrical energy is applied to the tissue or to conductive media in proximity to the tissue. The electrical energy can heat, evaporate and ionize the tissue.
Most commonly in electrosurgery, the electrical energy is applied as a continuous wave (CW) or pulses of radiofrequency energy. The RF energy is applied with a probe having a pair (or more) of electrodes. Tissue in proximity to the electrodes is heated and destroyed or ablated. Electrosurgery with RF energy is usually used in medical procedures where direct heating is desired for tissue modification, destruction, or removal. Examples of such procedures include coagulation of blood vessels, tissue dissection in general surgery (electric knife), and skin and cartilage removal.
A shortcoming of using RF energy in electrosurgery is that, for some applications, the RF energy heats too broad a region, resulting in undesired collateral damage to surrounding tissues. Use of RF energy is particularly undesirable for delicate microsurgical procedures where RF energy tends to result in unacceptably large areas of collateral damage.
Certain pulsed electrosurgical devices have been proposed for specific applications. R. Vorreuther et al. Journal of Urology, 153:849-853 (1995) use high energy pulses (tens of milliJoules) with a relatively long duration (hundreds of microseconds) to generate shock waves which destroy the targeted tissue (e.g. kidney stones). The method of Vorreuther obviously cannot be applied to delicate microsurgical procedures. Also, the long pulse durations taught by Vorreuther tend to result in excessive collateral damage. Another disadvantage of the teachings of Vorreuther is that the device has a short lifetime of less than 100 pulses due to the high energy of the pulses.
U.S. Pat. No. 4,429,694 discloses an electrosurgical technique where AC voltage pulses are used to coagulate tissues by heat generation. The AC pulses generate plasma in air which is applied to the tissues to be coagulated. U.S. Pat. No. 5,300,068 teaches the use of relatively long duration pulses (about 200 microseconds) for electrosurgery. U.S. Pat. No. 5,509,916 discloses the combination of laser pulses and electrical pulses. The laser pulse provides more precise localization of the electrical discharges. The prior art does not teach methods for precise electrosurgical cutting of tissues applicable to microsurgery in liquid where a very small (tens of microns or less) collateral damage zone is important.
"Electrical Alternative to Pulsed Fiber Delivered Lasers in Microsurgery", Journal of Applied Physics 81(11): 7673-7680 (1997) by Daniel Palanker et al. discloses a method for intraocular microsurgery based on cavitation bubble generation by electrical discharge. In this approach, the expanding cavitation bubble is used to provide cutting action. A limitation of using the cavitation bubble for cutting is that only very soft tissues (e.g. retinal tissues) can be cut. Relatively hard tissues such as eye lenses, lens capsules (e.g. in a capsulotomy procedure) or irises cannot be cut by the method disclosed by Palanker. Yet another disadvantage of the method of Palanker is that cavitation bubbles produce substantial collateral damage to surrounding tissues due to generation of water flow during bubble collapse.
Pulsed lasers have commonly been used in delicate surgical procedures where collateral damage must be avoided (i.e. vitreoretinal surgery). However, a great disadvantage of laser-based devices is that they are relatively expensive, costing upwards of $100,000. Electrosurgical systems are typically much less expensive.